Injection moulds for transparent parts

Precision moulds for optical components, lenses and transparent housings

The injection moulds for transparent parts are the most technically demanding: less dust, solder line Your veil renders the part non-compliant. Hybster designs specialised tooling for optical parts, lenses, light guides, transparent cosmetic housings and protective screens, using highly polishable steels (SPI A1 mirror polished), with hot channels to sealing and fine thermal regulation.

Our expertise covers the main transparent materials (PC, PMMA, SAN, COC, COP) for critical sectors: lighting, automotive, consumer electronics, luxury cosmetics, medical.

Pourquoi les pièces transparentes nécessitent un moule spécifique ?

A transparent room exposes all internal flaws: bubbles, weld lines, sheer, micro-stripes, Reassurances, particles. Where a flaw would be invisible on an opaque part, it becomes glaring on a transparent part. The mould must therefore be designed specifically to avoid them:

• SPI polishing A1 (mirror) mandatory on all the impressions to provide a smooth surface to the part.
• Fine-grained special steels (1.2316 ESR, M333, Stavax 420) porosity-free, capable of accepting a homogeneous mirror polish.
• Careful ventilation to perfectly evacuate air and avoid bubbles or burns.
• Hot runner shut-off nozzles To eliminate injection point marks visible through the material.
• Conformal cooling for a Cooling perfectly uniform, removing the internal stresses responsible for veil.

To understand the process for injecting transparent materials, please consult our dedicated article: Fabrication of transparent polycarbonate parts for lighting.

Injectable transparent materials and their specificities

PMMA (Polymethyl methacrylate)

PMMA (Plexiglas, Altuglas) offers the purest transparency (transmission 92%), excellent UV and scratch resistance. Ideal for optical applications, signage and decorative screens. Less impact-resistant than PC. See our PMMA datasheet.

PC (Polycarbonate)

PC offers transparency (88%) and exceptional impact resistance. Widely used in lighting (LEDs, spotlights), electronic enclosures and protective equipment (visors, helmets). More susceptible to scratches than PMMA. See our Subject sheet PC.

SAN (Styrene Acrylonitrile)

Acrylic (SAN) is a cost-effective alternative to PMMA for decorative or consumer applications. Slightly lower transparency, good rigidity, attractive price.

COC / COP (Cyclo-olefins)

High-performance materials for demanding medical and optical applications: excellent clarity, low birefringence, dimensional stability, chemical resistance. More expensive but essential for precision optics (intraocular lenses, medical vials).

Technical specifications of the mould

• ESR steels (Electroslag Refining) with no inclusions or porosity, perfect polish.
• SPI Polishing A1 in several steps (P800 → P1500 → P3000 → 3 μm diamond → 1 μm).
• Hot runner with valve gates for PI invisible.
• Optimised cooling for multiple drillings or conformal cooling on large surfaces.
• Ejectors outside the aspect area, flat-profile or sleeve-type so as not to leave marks.
• Clean room recommended for mould manufacturing and storage (dust = critical defects).

Common applications

• Lighting LED light guides, projector optics, diffusers.
• Automotive Headlights, indicators, light clusters, parcel shelves.
• Consumer electronics screens, buttons, product portholes.
• Luxury cosmetics bottles, cases, mascara tubes, cream jars.
• Medical syringes, tubes, vials, viewing windows for medical devices.
• Household Transparent lids, coffee machine windows.

Our method

1. Optical and functional study

For optical components (lenses, light guides), we work with your optical designer to ensure that the mould accurately replicates the optical surfaces (spherical, aspheric, freeform). Typical form tolerances: ± 0.01 mm on optical areas.

2. DFM-specific transparency

Advanced rheological analysis to anticipate and position weld lines outside visible zones, precise sizing of runner channels, verification of venting in each critical zone. Systematic Moldflow simulation.

3. Fabrication by expert moulders

Moulds for transparent parts are entrusted to specialist mould-makers (France, Germany, Switzerland, Italy) who are proficient in SPI A1 polishing. The lead time includes several stages of progressive polishing, with systematic checks between each stage.

4. Development in clean press

The mould trial is carried out under controlled cleanliness conditions with rigorous drying of the material (PC is highly sensitive to moisture). The development phase is longer (3 to 7 days) to optimise all parameters and ensure a very low scrap rate.

Indicative costs and timescales

• Clear simple part mould, SPI A2 polish £18,000 to £35,000, 10 to 14 weeks.
• Premium SPI A1 mould + hot runner valve gate €35,000 to €75,000, 14 to 18 weeks.
• High-precision optical mould (lens, light guide) €50,000 to €150,000, 16 to 24 weeks.
• Multi-cavity mould for large series, transparent €80,000 to €250,000+, 18 to 26 weeks.

To go further

• Supplementary article: fabrication de pièces transparentes en Polycarbonate.
• For visible non-transparent parts: moulds for visible parts.
• Two-material Two-component injection moulding.
• Full offer: plastic injection moulds.